Screw rotor machine for compressible media

ABSTRACT

A screw profile machine for compressible media, in which the profile of the head of the lobes of a driving rotor is formed by two portions of epicycloids interconnected by a conjugating curve. The rear portion of the conjugating curve, as viewed in the direction of the driving rotor rotation, is a portion of an elongated hypocycloid formed as a result of oscillations of a generating circumference along the inner side of the initial circumference of the driving rotor with a point disposed outside the generating circumference whose radius is greater than zero but is smaller than the radius of the initial circumference of the driving rotor, and the front portion of the conjugating curve, as viewed in the direction of the driving rotor rotation, is essentially an arc of a circumference.

United States Patent [1 1 Amosov et al.

[ SCREW ROTOR MACHINE FOR COMPRESSIBLE MEDIA [76] Inventors: PavelEvgenievich Amosov,

Kronverkskaya ulitsa, 29/37, kv. 87; Leonid Mikhailovich Imyanitov, 6-yaSovetskaya ulitsa, 33, kv. 4; Vitaly Konstantinovich Smekhov, ulitsaKolomenskaya, 33/40, kv. 25; Valery Leonidovich Troiimov, ulitsaMatrosova, l2, kv. 8, all of Leningrad; Avely Isaich Shvarts, ulitsaKosmonavtov, 3, kv. 45; Vladimir Borisovich Shnepp, ulitsa Zarya, 4, kv.5, both of Kazan, all of USSR.

22 Filed: Oct. 20, 1970 211 Appl. No.2 82,296

[30] Foreign Application Priority Data Oct. 20, I969 U.S.S.R .1 1367354[52] US. Cl. 418/201 [51] Int. Cl ..F01c l/16, F010 1/24, F04c 1/10,

[58] Field of Search 418/201, 202, 203,

11] 3,738,783 June 12, 1973 [56] References Cited UNITED STATES PATENTS6/1949 Whitfield l/l969 Schibbye [57] ABSTRACT A screw profile machinefor compressible media, in which the profile of the head of the lobes ofa driving rotor is formed by two portions of epicycloids interconnectedby a conjugating curve. The rear portion of the conjugating curve, asviewed in the direction of the driving rotor rotation, is a portion ofan elongated hypocycloid formed as a result of oscillations of agenerating circumference along the inner side of the initialcircumference of the driving rotor with a point disposed outside thegenerating circumference whose radius is greater than zero but issmaller than the radius of the initial circumference of the drivingrotor, and the front portion of the conjugating curve, as viewed in thedirection of the driving rotor rotation, is essentially an arc of acircumference.

2 Claims, 1 Drawing Figure PATENIEU JUN 1 2191s SCREW ROTOR MACHINE FORCOMPRESSIBLE MEDIA BACKGROUND OF THE INVENTION The present inventionrelates to devices for compressing compressible media, or for convertingthe energy of compressed media into a mechanical one and, moreparticularly, to screw rotor machines.

Known in the art is a screw rotor machine comprising a body and drivingand driven rotors installed in the body and interacting with each otherand the body. The profile of the head of the lobe of the driving rotoris formed in its butt end section by two portions of epicycloidsinterconnected by a conjugating curve, with the front portion of thelobe head, as viewed in the direction of the driving rotor rotation,being formed by a part of the epicycloid and a conjugating curve whichis essentially an arc of a circumference with its center disposed on aninitial circumference of the driving rotor, and the rear portion of thelobe headbeing formed by a part of the epicycloid. I

The profile of the flank of the lobe of the driven rotor is conjugatedwith respect to the profile of the head of the lobe of the drivingrotor.

Compression of the gas in the machine is due to a decrease in the volumeof spaces isolated from the suction pipe branch. These spaces areconfined by the surfaces of the driving and driven rotors and thesurface of the body which is essentially a surface of two straightintersecting cylinders having parallel axes.

To hermetically seal the spaces of the rotors at the moments when themedium is supplied and discharged, it is necessary that the surfaces ofthe rotors and the body should contact eachother, and the total line ofthe contact should be continuous.

The conventional machine is disadvantageous in that there are jammedvolumes at the sides of the medium supply and discharge, which areformed in the case of a continuous line of contact. The jammed volumesresult in the formation of pulsating loads acting on the bearings andsynchronizing gears, and decrease the efficiency and reliability of themachine.

Another disadvantage of the machine lies in the fact that the areaconfined by the lines of the rotors engagement exceeds the area of thecavity between the adjacent lobes of the driven rotor. This results inthe driven rotor being loaded with a torque constituting approximately20 percent of the turning moment applied to the driving rotor of themachine, and decreases the reliability of the machine.

An object of the present invention is to provide a screw rotor machine,in which the profile of the head of the lobe of the driving rotorensures a decrease of the jammed volumes and unloading of the drivenrotor of the turning moment.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWING The followingdescription of an exemplary embodiment of the present invention is givenwith reference to the accompanying drawing which diagrammatically showsa cross section of a screw rotor machine according to the invention.

DETAILED DESCRIPTION OF THE INVENTION A screw rotor machine has drivingand driven rotors 2 and 3 respectively mounted .in a body 1. Lobes 4 ofthe driving rotor 2 consist mainly of heads only, while lobes 5 of thedriven rotor 3 consist mainly of legs or flanks only. The number of thelobes 4 of the driving rotor 2 should not be less than two and thenumber of lobes 5 of the driven rotor 3 less than three.

In the butt end section, the profile of the head of the lobe 4 of thedriving rotor 2 is not symmetrical to a radial line described to thepeak of lobe D and is formed by two portions A C and A,C of epicycloids,portion C D of an elongated hypocycloid and are C D, of thecircumference.

The rear portion of the lobe 4, as viewed in.the direction of thedriving rotor 2 as indicated by the arrow, is formed by portion A,C ofthe epicycloid and portion C D of the elongatedhypocycloid. The frontportion of the lobe 4, as viewed in the direction of rotation of thedriving rotor 2, is formed by portion ARC, of the epicycloid and are CD,of the circumference.

The epicycloids A,C, and A C, are formed as a result of oscillation of agenerating circumference 6 along the outer side of an initialcircumference 7 of the driving rotor 2. Describing points A and A aredisposed on the generating circumference 6.

The portion of the elongated hypocycloid GD is formed as a result of theoscillation of a generating circumference 8 along the inner side of theinitial circumference 7 of the driving rotor 2 by describing point Sspaced from the center of the generating circumference 8 over a distanceequal to the sum of the height of the head of the lobe 4 and the radiusof the generating circumference 8.

The line of engagement of the driving and driven rotors 2 and 3respectively is closed and is formed by curves which are essentiallytrajectories of points A and S The are C,D is formed'by a radius whichis smaller than the radius of circumference 9 of the projections of thedriving rotor 2.

When the radius forming the arc C D, is of a certain length, theepicycloid C 'D may have no portion on the front side of the lobe 4 andthe profile of the latter is formed in this case by the following threecurves: a portion of the epicycloid A,C a portion of the elongatedhypocycloid C,D and the arc of the circumference C D The radius of thearc C D of the circumference may exceed the height of the head of thelobe 4, in which case the center of the arc C 'D will be disposed insidethe initial circumference 7 of the driving rotor 2.

During the screw rotor machine operation the medium filling up thespaces confined by the surfaces of the driving and driven rotors 2 and 3and the surface of the body 1 changes its volume in the course ofrotation of said rotors and is moved from the inlet pipe branch of thescrew machine to the outlet pipe (not shown in the drawing).

Hence, due to the fact that the profile of the head of the lobe 4 of thedriving rotor 2 consists of a portion of an elongated hypocycloid and anarc of a circumference smoothly joined to each other and to the portionsof the epicycloids, and is oriented relative to the compressors so thatthe rear portion of the head of the lobe, as viewed in the direction ofrotation of the driving rotor, is formed by portions of an elongatedhypocycloid and epicycloid, there is provided a decrease in the jammedvolumes at the side of the inlet and outlet of the screw rotor machine,thereby resulting in decreased pulsating loads acting on the bearingsand synchronizing gears and increased efficiency of the process ofcompression (expansion) of the medium and higher reliability of themachine.

In addition, in the present screw rotor machine, the difference betweenthe area confined by the line of engagement of the lobes of the rotorsand the area of the cavity of the driven rotor in the butt end sectionis decreased, as a result of which the driven rotor is relieved of theturning moment and the contact stresses between the lobes of the rotorsor, in the case of employment of synchronizing gears, the contactstresses acting on the teeth of the gears are reduced, thus promoting agreater reliability of the machine operation.

With the center of the arc of the circumference forming the frontportion of the profile of the head of the lobe disposed inside theinitial circumference of the driving rotor, the driven rotor iscompletely relieved of the turning moment.

The profile of a lobe is understood as a line along which the surface ofthe lobe intersects the plane perpendicular to the axis of rotorrotation. The head of a lobe is a part of the lobe profile locatedbeyond the limits of the initial circumference 7 of the rotor 2. Thelocation of the curves A,C,, C,D D,C,' and C A, on the profile of a lobehead and their orientation relative to the direction of rotationdetermines the quality of the rotors as working components of screwrotor machines. This necessitates the use of the terms the front portionand the rear portion of a lobe (in the direction of rotation).

What is claimed is:

1. A screw rotor machine for compressible media, preferably acompressor,.comprising a body; a driving rotor mounted in said body; atleast one driven rotor mounted in said body and coacting with saiddriving rotor, said driving rotor having an initial circumference and atleast two lobes extending from the initial circumference, each lobeshaving a profiled head defined by two portions of epicycloidsinterconnected by a conjugating curve, a rear portion of said curve, asviewed in the direction of said driving rotor rotation, beingessentially a portion of an elongated hypocycloid formed as a result ofoscillation of a generating circumference along the inner side of theinitial circumference of said driving rotor with a point disposedoutside said generating circumference whose radius is greater than zerobut is smaller than the radius of said initial circumference of saiddriving rotor, and a front portion of said conjugating curve, as viewedin the direction of said driving rotor rotation, being essentially anarc of a circumference.

2. The screw rotor machine as claimed in claim 1, in

which the center of said arc of the circumference is disposed insidesaid initial circumference of the driving I'OIOI.

1. A screw rotor machine for compressible media, preferably acompressor, comprising a body; a driving rotor mounted in said body; atleast one driven rotor mounted in said body and coacting with saiddriving rotor, said driving rotor having an initial circumference and atleast two lobes extending from the initial circumference, each lobeshaving a profiled head defined by two portions of epicycloidsinterconnected by a conjugating curve, a rear portion of said curve, asviewed in the direction of said driving rotor rotation, beingessentially a portion of an elongated hypocycloid formed as a result ofoscillation of a generating circumference along the inner side of theinitial circumference of said driving rotor with a point disposedoutside said generating circumference whose radius is greater than zerobut is smaller than the radius of said initial circumference of saiddriving rotor, and a front portion of said conjugating curve, as viewedin the direction of said driving rotor rotation, being essentially anarc of a circumference.
 2. The screw rotor machine as claimed in claim1, in which the center of said arc of the circumference is disposedinside said initial circumference of the driving rotor.